A mid-wheel drive moving device has the feature of a small radius of gyration, and is applied to a wheelchair that is used in a small space (such as, an indoor space). The moving device has a pair of middle wheels driven by different drive motors respectively. By controlling the pair of middle wheels at different rotational speeds or the same rotational speed, the moving device can torn left or right or move forward or backward.
The related prior art includes U.S. Pat. No. 5,944,131 titled “mid-wheel drive power wheelchair”, U.S. Pat. No. 7,828,310 titled “chassis structure for mid-wheel drive power wheelchair”, U.S. Pat. No. 6,070,898 titled “suspension system for a wheelchair”, and so on.
These mid-wheel drive moving devices are usually equipped with front and rear auxiliary wheels to increase the stability of the movement so as to avoid turnover. However, in some situations, these auxiliary wheels may excessively increase the load of the drive wheels (middle wheels), which may easily cause overloading of the drive motors. For example, when the front auxiliary wheels are at a higher position relative to the drive wheels and the user controls the drive wheels to steer, the front auxiliary wheels and the rear auxiliary wheels cannot move smoothly because they are not in contact with the ground, so that when the drive wheels are steered in this situation, the front and rear auxiliary wheels form an obstruction to increase the load of the drive wheels. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.